Changing Views About A Changing ClimateWhat is the role of humans in climate change? "Call me a converted skeptic," physicist Richard Muller wrote in an Op-Ed in the New York Times this week, describing his analysis of data from the Berkeley Earth Surface Temperature project. Though Muller was once a notable skeptic regarding studies connecting human activity to climate change, he has now concluded that "humans are almost entirely the cause" of global warming.

What is the role of humans in climate change? "Call me a converted skeptic," physicist Richard Muller wrote in an Op-Ed in the New York Times this week, describing his analysis of data from the Berkeley Earth Surface Temperature project. Though Muller was once a notable skeptic regarding studies connecting human activity to climate change, he has now concluded that "humans are almost entirely the cause" of global warming.

IRA FLATOW, HOST:

This is SCIENCE FRIDAY. I'm Ira Flatow. This week, physicist Richard Muller published an op-ed piece in the New York Times in which he said that humans are almost entirely the cause of global climate change. This is following his own analysis of Earth's surface temperature data.

What makes the op-ed notable is Dr. Muller was once openly skeptical of studies linking global warming to human activity, and now, well, call me a converted skeptic, he wrote. He joins us now to talk about it. He is professor of physics at the University of California at Berkeley and a faculty senior scientist at Lawrence Berkeley National Laboratory, author of the new book "Energy For Future Presidents: The Science Behind the Headlines." Welcome back, Dr. Muller.

RICHARD MULLER: Good to be here, Ira.

FLATOW: So tell us about your change of mind and heart about this issue.

MULLER: Well, if you had asked me a year ago, I might have said I didn't know whether there was global warming at all. But we had begun a major study, scientific reinvestigation. We were addressing what I consider to be legitimate criticisms of many of the skeptics.

But about nine months ago, we reached a conclusion that global warming was indeed taking place, that all of the effects that the skeptics raised could be addressed, and to my surprise, actually, the global warming was approximately what people had previously said.

It came as a bigger surprise over the last three to six months when our young scientist Robert Rohde was able to adopt really excellent statistical methods and push the record back to 1753. With such a long record, we could then separate out the signatures of solar variability, of volcanic eruptions, of El Nino and so on. And actually, to my surprise, the clear signature that really matched the rise in the data was human carbon dioxide and other greenhouse gases. It just matched so much better than anything else. I was just stunned.

FLATOW: You know, you wrote in your book, even, page 75: The evidence shows that global warming is real, and the recent analysis of our team indicates that most of it is due to humans.

MULLER: (Technical difficulties)... And then we had these new results. I was much more cautious in the version of the book that was sent around for pre-review, and then we managed to get the new results in the new book.

FLATOW: You know, you've been criticized on both sides of the aisle, as they say now. I think some scientists are saying: Why did you publish - why didn't you publish it in legitimate, peer-reviewed journals first?

MULLER: Oh, we're following the - I mean, we're following the tradition of science, which is that you distribute this widely to your peers before you publish it. Jim Hansen does the same thing. He puts his papers online. This is a tradition in the field.

Peer review means you present results in a public forum, you distribute pre-prints. Most of my important papers were widely distributed to other scientists far before they appeared. It's the best kind of peer review.

FLATOW: And you challenge anyone to come up with a better explanation.

MULLER: I do, and we have this record going back to 1753. That's pre-Revolutionary War. Some of the early measurements in the United States were taken by Benjamin Franklin and Thomas Jefferson. So we have this excellent record now. We use essentially all the data, nobody had previously used more than about 20 percent of the temperature stations. So we have this excellent record. And given that excellent record, now you say, where does it come from?

A real surprise to me was that when we compare to this to the sun-spot record, which shows the solar variability, there's no match whatsoever. The variability of the sun did not contribute. I think that was the primary alternative explanation, and now with this really long record, thanks again to Robert Rohde, we really can eliminate that. And there's not much left.

We see the volcanoes very clearly. We see the volcanic eruptions, but their effect is always short-lived, about three or four years.

FLATOW: And yet you say that even though you can accept the CO2-temperature connection and that humans are behind it, you say that some people are still too ready to connect various weather events to climate change.

MULLER: Well, that's true. I believe that many people who are deeply concerned about global warming feel that the public needs something more dramatic. And so take example the - NOAA recently announced that the last 12 months were the warmest on record in the United States. When I heard that, I looked it up, and sure enough they're right. We see that in our own record. But remarkably, the world had cooled somewhat in that period. It was just the United States, which is two percent of the globe.

I feel that one has to be a little bit more candid with the public, and to ascribe the warming of the United States not as a heat wave but as global warming, when the globe is cooling, is not being completely up front.

FLATOW: Well, if the globe is...

MULLER: The public is smart. They don't like to be fooled.

FLATOW: If the globe is cooling, then what is global warming, then?

MULLER: Oh, I just mean the globe has been cooling for the last three or four years.

FLATOW: I see.

MULLER: As we said, a heat wave in the U.S., but it wasn't a world event that set that heat wave.

FLATOW: How - let me just change gears because the title of your book is "Energy for Future Presidents: The Science Behind the Headlines." The last time you were on, you were talking about physics for future presidents. We're in a presidential debate year. Do you think this should be an issue, the talk about global climate change and global warming?

MULLER: Oh I - energy, there's nothing more important in our world than the future of energy. We start wars over energy. Events like Fukushima and the Gulf oil spill have too much influence in our policy. We have to sit back and be thoughtful and think: What can we do?

For the case of global warming, I do believe we should take action, but most of the action that people are suggesting will not address the problem, and so we have to get the energy policy right. It has to be based in science and engineering and technology.

FLATOW: And what should that policy be? What should we do?

MULLER: The most important thing, there are two things that are really important. One is there's an enormous amount that can be done with energy efficiency and conservation: better automobiles, better insulation in homes. The second thing that we need to do, and this is equally important, is to recognize that natural gas emits one-third the carbon dioxide of coal.

And the future emissions, unfortunately, are not within the U.S. control. By the end of this year, China will be emitting twice the carbon dioxide as the U.S., and they're growing rapidly whereas our carbon dioxide emissions have been going down over the last few years.

So unless we can devise an approach where China can reduce its emissions, it won't do any good. Fortunately, there is that approach because China is building essentially one new coal gigawatt every week. That's a huge growth, and it's responsible for their increase in emissions, but they have good natural gas resources.

We have to develop and devise methods for clean fracking. Clean fracking is the key. They have enormous reserves over there. If they can switch from coal to natural gas, that'll have as big an effect as worldwide energy conservation and energy efficiency.

FLATOW: Do you think that your change of position might effect any other changes of positions among people possibly in Congress, some people who believe that global warming is the greatest hoax perpetuated on the human race?

MULLER: Well, I have great sympathy for such people because many of them, and I've talked to them in Congress, they knew there are legitimate concerns. They knew the data, not all the data had been used, it had been selected. They knew there had been adjustments to the data. They knew that a large number of the stations were poor quality. I've testified in Congress about this.

I think they had legitimate concerns. We need to respect the people who have been skeptical. What - I don't think changing my opinion will have a big impact. I think the work that we did - we have posted our papers online for scrutiny. They have actually undergone a lot of peer review. They have been submitted to journals. We've gotten peer review back, and we've responded to it. We hope they'll be published soon.

But in the meanwhile, they are available online. We've put the data available online, we've put all of our programs online. We have an utter transparency that I hope is setting a new standard for how transparent you can be. In the end, I hope it is the work we did that will convince people, not the fact that I've changed my mind.

FLATOW: And where do you go from here? Is there anything next on your agenda about global warming?

MULLER: Well, I think the issue of policy is really important. And we have been looking very hard about what can be done. In my new book, we talk about how much money can be made by using energy efficiency, energy conservation, I called it energy productivity.

The fact is just for the ordinary citizen, as well as the Chinese, a little bit of money placed in insulation in your home can yield a return on your investment that exceeds that of Bernie Madoff. And not only that, it's legitimate, and it's even tax-free because you don't pay taxes on money you save.

So that, and unfortunately too many people in the community, too many of my friends who are worried about global warming, have already taken a position on fracking. The fact is that natural gas can be made clean. It's not hard. It's much easier to do clean fracking than it is, for example, to make cheap solar.

So I'm hoping that the environmentalists who have started to oppose fracking, I think prematurely, can be won over and recognize that this has to be part of a worldwide energy policy. Natural gas also helps the Chinese because their citizens are being choked by the soot and other emissions of their coal plants.

So expediting a shift, this should be U.S. policy, that we will help the Chinese make the shift from coal to natural gas. China, India, the developing world, this is absolutely essential.

FLATOW: And what about a shift to renewables?

MULLER: Well, that's wonderful, and that will ultimately take the place of natural gas, but take China for example. Last year, they installed what everybody says was a gigawatt of solar. In fact, it wasn't a gigawatt because that's the peak power. Average in night, and it's half a gigawatt. Average mornings and late afternoons, it's a quarter of a gigawatt.

Meanwhile, they put in 40 gigawatts of coal. So renewables are great, but for the developing world, they're still too expensive. And so China and India are going the way they can afford. We can't criticize them for that, and we can't afford to subsidize them. So the switch to natural gas I think is absolutely essential for the next several decades.

FLATOW: All right, thank you very much, it's been enlightening to talk to you, and hope that you'll be back when you've got new data to share with us.

MULLER: We'd be happy to come back any time, Ira.

FLATOW: Richard Muller, thank you. He's author of "Energy for Future Presidents: The Science Behind the Headlines." He's also senior scientist at Lawrence Berkeley National Laboratory. And we're going to take a break, and when we come back, we're going to talk about planetary science of another kind, a trip to Mars.

This weekend, there are little Mars parties going on all over the country, waiting for the landing of a new Mars Rover Sunday night into early morning Eastern Time. So when we come back, John Grunsfeld from NASA is here to talk about it, 1-800-989-8255 is our number. You can tweet us @scifri, @-S-C-I-F-R-I or go to our website at sciencefriday.com. Stay with us, we'll be right back after this break.

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